The majority of fabrics comprise microbiologically degradable material. They are frequently made either wholly or partly of microbiologically degradable fibers, as for example of cotton, cellulose, e.g., viscose, lyocell (e.g., Tencel®), hemp, flax, linen, silk or wool. Fabrics made from synthetic fibers as well, such as from polyester, polyacrylonitrile, polyamide or polypropylene, are regularly colonized by bacteria. Fabrics made from synthetic fibers are colonized especially when they comprise finishing agents, such as softeners, water repellents, antistats and/or binders, for example, or when in the course of their use they pick up microbiologically degradable material, such as organic substances from perspiration or from the environment, for example.
Particularly with synthetic fabrics, as for example with polyester fabrics, it is observed that bacteria adhere to the fabric or fiber and form what is called a biofilm. This biofilm and the bacteria it contains can often not be fully removed on laundering, particularly at the low wash temperatures recommended for polyester fabrics. As a consequence, bacteria remain on the fabric, and may become active when it is worn again and may then result in an increasingly rapid formation of unpleasant odors. This problem brings about an ever greater reduction in the wear time of polyester textiles over the course of time, and often results in an inability for the unpleasant odor of such textiles to be removed completely after a number of wear cycles, in spite of washing. Within technical circles, this phenomenon is well known and is often referred to as “old perspiration odor”.
A biofilm is understood in general to be an assembly of microbial cells which are connected to a substrate surface and which are embedded in an extracellular polymeric matrix (e.g., of exo-polysaccharides), which is normally formed by the microbial cells themselves.
The microbial colonization of substrates and the formation of a biofilm normally include the adhesion of microorganisms, especially bacteria, an example being the widespread Pseudomonas sp., as a first, critical step. The bacteria or the protein structures of the bacterial envelope adhere to various surfaces usually via unspecific hydrophobic interactions (e.g., Van der Waals' interactions).
Through the release of polymeric substances, especially exo-polysaccharides, over time, the accreted bacteria form a fully-developed biofilm (also referred to as bioslime or slime layer). This biofilm is frequently highly resistant to the use of active antimicrobial ingredients, since the slime layer in general is of low permeability and the microorganisms are embedded in the slime layer. Preventing the initial adhesion of bacteria to surfaces is therefore a preferred approach in the control of bacteria and the prevention of biofilm formation.
An advantage of an antiadhesion coating (often also called an antifouling coating) relative to finishing with active antimicrobial ingredients which directly kill bacteria or inhibit their growth, moreover, is that it is possible to use eco-friendly compounds that are not toxic, such as polymers, for example. It is therefore possible to do largely without the use of biologically active ingredients which are often problematic to humans.
Antifouling coatings for reducing the adhesion of microorganisms to solid substrates have been known for a long time, particularly in the medical sector or as a protective coating for ships. Described in the prior art, for example, are antifouling coatings comprising polyethylene glycol (PEG)-based polymers, as for example in M. Chamley et al. (Reactive & Functional Polymers 71 (2011), 329-334), Kingshott et al. (Langmuir 2003, 19, 6912-6921) or WO 2008/089032.
Document WO 2003/024897 describes a method for coating surfaces, especially hydrophobic surfaces, with specially designed thioethers and amphiphilic thioethers.
Document WO 2008/049108 describes multifunctional biocoatings and methods for employing them. The surface-modifying agent (SMA) may for example comprise dopamine or dopamine derivatives. WO 2008/089032 is directed to an antifouling coating with a modified polyethylene glycol (PEG) polymer, e.g., a dopamine-modified PEG polymer such as PEG-DOHA4.
The publication of Tsibouklis et al. (Contact Angle, Wettability and Adhesion, Vol. 4, 2006, 461-469) describes the formation of biofilms on substrates and compares antifouling coatings made from poly(fluoroalkyl (meth)acrylates) and poly(meth)acrylates.
Document US 2010/0112364 describes a method for coating various substrates, such as metals, fabrics and plastics, where the surface of the substrate is oxidized, after which an unsaturated monomer is applied and polymerized. The coating is said to reduce the adhesion of biological material.
The coating methods described in the prior art are either technically complicated and/or costly in their implementation, and/or yield an antiadhesive coating which lacks adequate effectiveness and stability. In particular, the methods described in the prior art are not capable of providing a stable (especially wash-stable) finish on fibers and/or fabrics that can be applied simply and inexpensively by means of common textile application techniques.
It is critical, moreover, for the development of a coating method of this kind that the antiadhesive activity of the fiber or fabric coating can be determined reliably and rapidly, particularly in a high-throughput process.
Described in the prior art are a multiplicity of methods for the quantitative determination of biofilm formation, and of methods for determining the biomass of an existing biofilm. In the medical sector in particular, such as with implants, the formation of biofilms, by microorganisms of the genus Staphylococcus, for example, is critical, since bacteria in a biofilm have fundamentally different properties than suspended bacteria—a greater resistance toward antibiotics, for example.
The publication of Srdjan S. et al. (APMIS, 115: 891-899, 9, 2007) describes the individual steps of a method for the quantitative determination of the formation of biofilm by Staphylococci in various microtiter plates, such as in microtiter plates which have been treated with tissue cultures, for example. A method is described wherein a biofilm is formed on the walls and bases of the microtiter plate and is stained directly in the microtiter plate by means of a suitable dye, such as with crystal violet, for example. The quantity of the accreted dye is evaluated by a suitable technique (e.g., using microtiter plate readers).
The publication of Peeters E. et al. (Journal of Microbiological Methods 72 (2008) 157-165) compares different methods for the quantitative determination of biofilms which have grown in a microtiter plate. One possibility described is that of direct staining in the microtiter plates of biofilms of P. aesuginaosa and S. aureus with different dyes, e.g., crystal violet, Syto9, and the possibility of evaluation by means of suitable spectroscopic methods.
The publication of Kingshott et al. (Langmuir 2003, 19, 6912-6921) describes a method for determining the adhesion of Pseudomonas sp. on modified PET plastics surfaces, where the number of accreted bacteria is determined by indirect conductometry on the basis of the carbon dioxide produced by the accreted bacteria. The publication of Ciag et al. (Langmuir 2012, 28, 1399-1407) describes a bacterial adhesion assay where the bacteria accreted on a PEG-modified surface are stained and examined by means of confocal laser scanning microscopy (CLSM).
The methods of determination described in the prior art are not suitable for fabrics and are often limited to specific microtiter plate systems. The prior-art determination methods often relate to methods in which the biofilm or the number of accreted bacteria is determined directly on the substrate, something which often necessitates a high level of cost and complexity in terms of apparatus and time.